Ingestible wireless medical capsules are known in the medical arts. Such capsules telemetrically transmit information to a receiving and recording apparatus located outside the body. The wireless capsule is swallowed and travels through the digestive tract, collecting and transmitting data during the course of its journey. Receiving and recording apparatus is stationed external to the body. In general, after a day or two, the disposable capsule is excreted naturally from the body and the recorded data, such as for example, temperature, pH, pressure, and transit time, may be transferred for analysis and/or storage. It is known in the art to use wireless medical capsules for collecting images by equipping them with cameras, or for delivering doses of medication to general areas of the digestive system by equipping them with drug reservoirs.
The deployment and detection of relatively small probes or sensors for reconnaissance in confined, inaccessible, or remote spaces is useful in many contexts. Determining the position of an object during deployment faces may challenges. In many applications, the target environment may be no more than a few liters in volume. It is sometimes desirable to determine the position of an object, such as a probe or sensor capsule. with as much precision as possible. Remote sensing may be used in many endeavors, such as industrial or medical applications. For example, the currently available wireless capsules used in the medical field are carried by peristalsis through the digestive tract, and the capsule location during the journey is either unknown or only approximately known. Similarly, in non-medical applications, a probe capsule may be carried by fluid flow and/or gravity, through a system of piping or tubing for example, and its position at any given time only approximated. The lack of position information is a drawback of current wireless capsule technology. For example, often a doctor reviewing data from an in vivo capsule does not know the precise location of features indicated by the data, e.g., an image of a gastro-intestinal tumor. Often an additional scoping procedure or even surgery may be required in order to determine the exact location of the problem. In connection with medical devices, some development of magnetic locating techniques has occurred. One approach, exemplified by U.S. Pat. No. 5,558,091 to Acker, is to embed a magnetic sensor in an in vivo capsule, and track the sensor within the body by relating it to magnetic fields external to the body. Although this approach may be useful to some degree, it does not take into account the effect of the earth's magnetic field or the potential interference of additional magnetic fields such as those which may emanate from electrical current and ferromagnetic materials nearby. Another approach, exemplified by U.S. Pat. No. 6,216,028 to Haynor, is to place a magnet on a medical device such as the tip of a probe inserted into the patient, and detect the magnet's field distribution with sensors located on an outside surface of the body. This approach proposes using four magnetic sensors to measure the magnetic field in the x, y, and z axes, and modeling the magnetic tip as a dipole, solving a number of nonlinear equations to determine the position of the magnetic dipole. The complexity of the computations involved require considerable computing power and/or a significant amount of time to complete. The complexity of this approach also increases the potential for considerable error.
Improved systems and methods for accurately determining the position of a remote object, such as a locatable wireless capsule or probe would be useful and advantageous in order to accurately match a location with remotely detected images or other parameters such as pH, temperature, pressure values and so forth. It may also provide advantages for accurately guiding the delivery of medications, or for taking biopsies, or for later surgery. In non-medical applications, it may be used for inspecting piping or fluid-handling systems. Used in conjunction with capsules or probes capable of controlled movement, the capability for timely detection of the probe or capsule position would be particularly advantageous. Due to the foregoing and other problems and potential advantages, improved position determining methods and systems using magnetic fields would a useful contribution to the applicable arts.